Color photographic elements typically contain several records each with silver halide sensitized to a different region of the visible light spectrum. Generally, one record is sensitized to red light, another green light and another, blue light. Each of the foregoing records also contains a color coupler which reacts with oxidized developer during processing of the element, to produce a dye in a pattern corresponding to the image to which the element was exposed. In a typical element the red, green and blue sensitive records respectively contain a cyan dye forming coupler, a magenta dye forming coupler and a yellow dye forming coupler.
As to the colour couplers, these are known to belong to a number of classes, for example magenta dye-forming couplers can be pyrazolones, pyrazolotriazoles and pyrazolobenzimidazoles while yellow dye-forming couplers can be acetanilides. European Patent Specification 0 431 374 A describes .beta.,.gamma.-unsaturated nitriles as cyan colour couplers of the general formula:
R.sub.2 --V.dbd.C (R.sub.1)--CH(W)--CN PA1 R.sub.1 is a substituent, PA1 V is nitrogen or --C(R.sub.3).dbd., PA1 if V represents nitrogen, R.sub.2 represents a substituent, PA1 if V represents --C(R.sub.3).dbd., R.sub.2 and R.sub.3 each represent a substituent, provided that at least one of R.sub.2 and R.sub.3 represent an electron attractive substituent, and provided that if R.sub.2 or R.sub.3 represents an aliphatic group or an aromatic group, the other does not represent an acyl group, and PA1 R.sub.1 and R.sub.2 may bond together to form a ring. PA1 RNH--C(CN).dbd.C(CN)--SO.sub.2 R. PA1 X is H or a group which splits off on coupling with oxidised colour developer, PA1 R is an alkyl, cycloalkyl, aryl or heterocyclic group any of which may be substituted, --COR.sup.1, --CSR.sup.1, SOR.sup.1, SO.sub.2 R.sup.1, --NHCOR.sup.1, --CONHR.sup.1, --COOR.sup.1, --COSR.sup.1, --NHSO.sub.2 R.sup.1 wherein R.sup.1 is an alkyl, cycloalkyl, or aryl group any of which are optionally substituted, and wherein two or more of A, B, R, and X optionally form part of a ring, PA1 Link is a linking group and PA1 n is 0, 1 or 2.
wherein W is hydrogen or an atom or group capable of being released when the compound is subjected to a coupling reaction with oxidised product of an aromatic primary amine derivative and is attached to a carbon atom having an sp.sup.3 electronic configuration,
The couplers of the above general formula are said to have less subsidiary absorption in the blue region of the spectrum. In support of this contention one drawing (FIG. 1) and a table of data are provided wherein the dye formed from Coupler 53 is compared to that from Comparative Compound (1)--a phenolic coupler.
The color couplers used in the photographic elements of the present invention, as described below, are distinct from those of European Specification 0 431 374A because, inter alia, the coupling position is a carbon atom having an sp.sup.2 electronic configuration and the compounds are .alpha.,.beta.-unsaturated. No examples of them appear in EP 0 431 374A, nor is any method of making them disclosed.
"Preparation and Reactions of 1,2-dicyano-1,2-disulfonylethylenes" by E. L. Martin, Journal of the American Chemical Society, Aug. 20, 1963 at page 2449, describes compounds of the formula:
The method of preparation means that only compounds having the --SO.sub.2 R can be prepared. In addition there is no disclosure of ballasted compounds.
It has previously been found that known magenta couplers may have a tendency to yellow in unexposed areas of the photographic element, following processing. This problem is frequently referred to as fresh D.sub.min yellowing. This results in an undesirable yellowing which is particularly evident in the white, unexposed areas of color papers incorporating such couplers. Previously, it has been found that certain organic polymers can be incorporated into silver halide elements to reduce dye fade, fresh D.sub.min yellowing, or yellowing after prolonged exposure to light, heat and humidityl. Useful materials and procedures are described in U.S. Pat. No. 3,619,195, U.S. Pat. No. 4,857,449, U.S. Pat. No. 4,916,050, U.S. Pat. No. 4,946,770, U.S. Pat. No. 5,001,045, U.S. Pat. No. 5,019,490, U.S. Pat. No. 5,047,314, U.S. Pat. No. 5,047,315, U.S. Pat. No. 5,071,738, U.S. Pat. No. 5,077,188, U.S. Pat. No. 5,100,771, U.S. Pat. No. 5,120,637 and also EP 276,319, EP 332,165, EP 324,476.
It is desirable then, to provide photographic elements which incorporate a color coupler with advantageous properties, and which elements also incorporate a stabilizer which is effective at reducing fresh D.sub.min.